Crystal growth, characterization and advanced study of the noncentrosymmetric superconductor Mo3_3Al2_2C

We report on the first successful growth of single crystals of the noncentrosymmetric superconductor Mo$_3$Al$_2$C obtained by means of a cubic-anvil, high-pressure and high-temperature technique. Composition, structure, and normal-state transport properties of the crystals were studied by means of X-ray diffraction, energy-dispersive X-ray spectroscopy, magnetic susceptibility and resistivity measurements as a function of temperature. Variations in critical temperature ($T_c$) between 8.6 and 9.3 K were observed, probably due to the slightly different carbon stoichiometry of the samples. Single-crystal X-ray refinement confirmed the high structural perfection of the grown crystals. Remarkably, the refined Flack parameter values for all the measured crystals using a $P4_132$ space-group model were consistently close to either 0 or 1, hence indicating that the considered crystals belong to two enantiomorphic space groups, $P4_132$ and $P4_332$. An anomaly in the resistivity is observed at about 130 K, most likely associated with the onset of a charge-density-wave phase. The superconducting properties (and in particular the symmetry, the amplitude and the temperature dependence of the superconducting gap) were studied by using - for the first time in this compound - point contact Andreev-reflection spectroscopy. The results confirm that Mo$_3$Al$_2$C is a moderately strongly-coupled superconductor with $2\Delta/k_BT_c \simeq 4$ and unambiguously prove that the order parameter has an s-wave symmetry despite the asymmetric spin-orbit coupling arising from the lack of inversion symmetry.Comment: 12 pages, 12 figures, revtex forma

Lab Scale Fixed-Bed Reactor for Operando X-Ray Absorption Spectroscopy for Structure Activity Studies of Supported Metal Oxide Catalysts

Lab scale fixed-bed reactor is applied for operando transmission X-ray absorption spectroscopy (XAS) for structure-activity studies of supported metal oxide catalysts under real reaction conditions. This setup includes many properties of an optimal fixed-bed reactor for operando transmission XAS studies. For instance, it is usable in a wide range of temperature (up to 1,000°C), pressure and space velocity. Besides, this operando setup can be used for transmission XAS measurements in a wide edge energy range. The potential of this reactor for operando transmission XAS is demonstrated by, as examples, the three-way catalytic performance of Pd/Al2O3/CeZrO2 and Rh/Al2O

One-step preparation of N-doped strontium titanate films by pulsed laser deposition

Perovskite-type oxynitrides exhibit promising electrical and optical properties and can possibly be used in the future as functional materials for electrical, photo-, and electrochemical applications. Continuous heterovalent substitution of oxygen ions by nitrogen ions allows tuning of the desired optical and/or electronic properties to the application specifications. In the present work deposition of SrTiO3:N films by pulsed reactive crossed beam laser ablation was studied in order to examine the influence of different deposition parameters on the film crystallinity and composition. The deposited films exhibit a perovskite-type crystal structure and reveals epitaxial growth on MgO(100) substrates. The unit cell parameters of the deposited SrTiO3:N films range within $3.9\underline{11}<a<3.9\underline{19}$ , which is slightly larger than for polycrystalline SrTiO3 (a=3.905). The studied films reveal an oxygen content in the range of (2.70-2.98)±0.15. The relative N content (vs. O) can be tuned within the range of 1.0-3.0% by adjusting the deposition parameters. The N:O concentration ratio increases with increasing laser fluence and target-to-substrate distances, while the substrate temperature has a more complex influence on the nitrogen concentration. In the range of 580-650°C the [N]/[O] ratio increases while further heating results in a gradual decrease of the N conten

RF-plasma assisted pulsed laser deposition of nitrogen-doped SrTiO3 thin films

Perovskite-type nitrogen substituted SrTiO3 thin films were deposited with a one-step process by RF-plasma assisted pulsed laser deposition from a SrTiO3 target using a N2 plasma, while deposition with a NH3 plasma yields films with almost no incorporated nitrogen. The deposited films exhibit a cubic perovskite-type crystal structure and reveal oriented growth on MgO(100) substrates. The unit cell parameters of the studied N-doped SrTiO3 films range within 3.905<a<3.918Å, which is slightly larger than for SrTiO3 (a=3.905Å). The nitrogen content in the deposited films varies from 0.2 to 0.7atom%. The amount of incorporated nitrogen in the films decreases with increasing RF-power, while the N2 flow rate does not have any pronounced influence on the N content. Nitrogen incorporation results in an increased optical absorption at 400-600nm, which is associated with N(2p) energy states that have a higher energy level than the valence band in strontium titanate. The optical band gap energies in the studied N-doped SrTiO3 films are at 3.2-3.3eV, which is very similar to that of pure strontium titanate (∼3.2eV). Films deposited with NH3 for the RF-plasma exhibit a lower degree of crystallinity and reveal almost no nitrogen incorporation into the crystal lattic

Process modelling of sugar mill biomass to energy conversion processes and energy integration of pyrolysis

ENGLISH ABSTRACT: The sugar industry over the years has been producing sugarcane bagasse as part of the sugar milling process. Currently this sugar mill biomass is incinerated inefficiently as a means of their disposal to produce steam and electricity, which in most cases are only just enough to supply the energy required to run the mills, thereby leaving very little or no extra energy for sale to bring in extra income in addition to sales revenue from sugar. However, the recent instability and uncertainties in the price of sugar and the global call for a green and sustainable environment have necessitated the search for ways of making effective use of this biomass to supply sugar mill energy demands, while producing extra energy in the form of electricity and other energy products for sale and at the same time contributing towards environmental sustainability. The main objective of this work was to develop process models for the processing of sugar mill biomass into energy and energy products. Based on this, biomass to energy conversion process (BMECP) models have been developed for various process configurations of two thermochemical processes; Combustion and Fast Pyrolysis using the Aspen Plus® simulation software. The aim of process modelling was to utilizing sugar cane bagasse as an input energy source to supply the energy requirements of two sugar mill configurations (efficient and less efficient mills), while generating extra electricity and high valued energy products for sale. Four BMECP configurations; 30bar BPST, 40bar CEST, 63bar CEST and 82bar CEST systems were modelled for the combustion thermochemical process. For the fast pyrolysis thermochemical process, two process configurations: Pure Fast Pyrolysis BMECP and Partial Fast Pyrolysis BMECP were modelled. The former BMECP utilizes all available bagasse through fast pyrolysis to produce bio-oil and biochar alongside generating electricity as well as energy to run the sugar mill operations. In the latter BMECP model, only surplus bagasse after separation of the quantity needed to supply the sugar mill energy requirement and electricity production is used to produce bio-oil and biochar. The technical performance of the BMECP models have been analysed and compared based on steam and electricity production rates, process efficiencies and environmental impacts (based on CO2 savings). The effects of boiler operating pressure and bagasse moisture content on the performance of the combustion based BMECP models have also been investigated. Finally, detailed economic models have been developed using the Aspen Process Economic Analyzer (Icarus®) to assess the economic viability of the BMECP models and sensitivity analysis performed to study the response of the BMECP models to variations in economic parameters. Technical performance analysis shows the combustion based BMECP models perform better than the Pure Fast Pyrolysis and Partial Fast Pyrolysis BMECP models with regards to steam and electricity production, thereby giving them higher electrical efficiencies. The electricity generation rate has been shown to increase with increasing boiler operating pressure and decreasing bagasse moisture content while steam production rate has been shown to increase with decreasing bagasse moisture content and decreasing boiler operating pressure. Despite the lower electrical efficiencies of the fast pyrolysis based BMECP models, the analysis shows that their overall process efficiencies compare very well with those of the combustion based BMECP models due to the production of high energy value pyrolysis products. Based on common operating pressure and 50% bagasse moisture content, the Pure Fast Pyrolysis and the Partial Fast Pyrolysis models have proved to be more environmental friendly with hourly CO2 savings of 40.44 and 41.30 tons for the Partial Fast Pyrolysis BMECP and the Pure Fast Pyrolysis BMECP respectively based on a 300 ton of sugarcane/h (81 ton bagasse/h) plant size. From an economic point of view, biomass combustion based on the 63bar CEST BMECP model has proved to be the most economically viable option under current economic conditions. First order total capital investment estimate for this BMECP is about $116 million, producing NPV of$390 million at the end of a 20 year plant life and IRR of 34.51%. The Pure Fast Pyrolysis BMECP model is the least economic viable option. Sensitivity analysis shows this BMECP model is the most sensitive to changes in bagasse and electricity prices; recording -191.61/+446.86% change in NPV for a ±30% change in bagasse price and -91.5/+338.60% for a ±30% change in electricity price.AFRIKAANSE OPSOMMING: Die afgelope jare het suikerriet-afval (bagasse) by suikermeule ‘n belangrik byproduk van die suiker-industie geraak. Tans word hierdie afval of biomasse verbrand in die suikermeule se poging om stoom en elektrisiteit op te wek; maar die die proses is oneffektief. Die hoeveelheid energie wat opgewek word, is skaars genoeg om die suikermeule self aan die gang te hou; daar is feilik geen sprake ‘n surplus energie waaruit ekstra inkomste verkry kan word toevoegend tot inkomste uit die suiker verkope self. Die huidige onstabiele suikerprys en gepaardgaande onsekerhede sowel as die werêldwye oproep vir ‘n groen- en volhoubare omgewing, noodsaak ‘n nuwe soeke na effektiewe manier om die afvalmateriaal sinvol te verwerk. Die tipe effektiwiteit van verwerking waarna gesoek word moet die volgende uitkomste hê: verskaffing van genoeg energie tydens produksie aan die suikermeuele self; vervaardiging van ekstra energie in die vorm van eletrisieteit en ander energie produkte. Terselfder moet die ook bydra tot die volhoubaarheid van die omgewing. Die grootste gedeelte van hierdie navorsing is gewy aan die ontwikkeling van “proses modelle” om suikemeule afval (bagasse) te omskep in energie en energie-produkte. Om hierdie doel te bereik, is biomassa-tot-energie omskeppingsproses- modelle (BMECP) ontwikkel om verskeie proses konfigurasies van twee termo-chemiese prosesse, naamlik Verbranding (Combustion), en Vinnige Pirolise (Fast Pyrolysis) deur die gebruik van die ‘Aspen Plus®’- simulasie sagteware. Die doel van die proses modelering was om suikerriet biomassa as ‘n bron van energie te gebruik om weer die energie benodighehede van twee denkbeeldige suikermeule vas te stel; een meul is voorgestel as effektief, die ander as minder effektief. Terselfdertyd is gekyk na die hoeveelheid ekstra energie wat elkeen sou opwek en ander hoogs waardevolle energie produkte om te verkoop (bv. ‘bio-olies en bio-char’). Vier “BMECP” konfigurasies (voorstellings) 30bar BPST, 40bar CEST, 63bar CEST en 82bar CEST sisteme is gemodelleer vir die Verbranding termo-chemiese proses. In die geval van die Pirolise (Pyrolysis) termo-chemiese proses, is twee proses konfigurasies gemodelleer: 1. Suiwer Vinnige Pyrolyise BMECP en 2. Gedeeltelik Vinnige Pirolise BMECP. In die geval van eersgenoemde, word alle beskikbare ‘bagasse’ deur vinnige pirolise omskep om ‘bio-olie’ en ‘bio-char’ te vervaardig.Verder wek dit ook elektrisiteit op so wel as die nodige energie om die suikermeule te laat opereer. In die geval van die Gedeeltlike Vinnige Pirolise BMECP , moet daar eers genoegsame ‘bagasse’ opsy gesit word om die suikermeule van genoegsame energie te voorsien vir die volle funskionering daarvan en elektrisiteit-opwekking. Van die surplus of oorblywende ‘bagasse’ kan dan gebruik word om ‘bio-olie’ en ‘biochar’ te produseer. Die tegniese prestasie van al die BMECP modelle is geanaliseer en vergelyk ten opsigte van stoom en elektrisiteits-opwekking; proses effektiewiteit asook die impak op die omgewing ( gebaseer op CO2 –besparings). Die effek van stoomkettel-druk tydens operering asook die bagasse se vog-inhoud. Op die prestasie van die verbrandingsgebaseerde modelle is ook ondersoek. Laastens, uitgebreide ekonomeidese modelle is ook ontwikkel deur die gebruik van die ‘Aspen Process Economic Analyser (Icarus®)’. Sodoende is die ekonomiese vatbaarheid van die BMECP modelle ondersoek. Hierdie sagteware help ook met. Sensitiwiteits-analise in die bestudering van die terugvoer van die BMECP modelle tot veranderlikes in ekonomiese parameters. Rakende effektiwiteit, toon die uitslae dat die verbrandings-gebaseerde BMECP modelle beter vaar as die met betrekking tot stoom- en elektrisiteits-opwekking. Verbrandings-gebaseerde-modelle toon hoër elektriese effektiwiteit. Indien die vog-inhoud van die bagasse laag was en die tempo van stoomketel operasie druk verhoog is, het die tempo van elektriesiteits-opwekking ook gestyg. Ten opsigte van stoom daarenteen, het die stoom-opwekking tempo verhoog in die die vogl inhou van diebagasse laag was asook verminderde stoomketel operering druk. Ten spyte van die laer elektriese effektiewiteit van die Suiwer Vinnig- en Gedeeltelik Vinnig BMECP modelle, dui die analise aan dat hul proses effektiewiteit in die geheel Goed vergelyk met die van die verbrandings-gebaseerde BMECP modelle. Dit is toe te skryf aan die produksie van die hoë-energie draende pirolise produkte. Gebaseer op algemene operering druk van 50% ‘bagasse’ vog-inhoud, het die bogenoemde twee modelle bewys om meer omgewings-vriendelik te wees met uurlikse CO2-besparings. In die geval van Gedeeltelike Vinnige Pirolise BMECP, 40.44 en vir die Suiwer Vinnige Pirolise BMECP 41.30 gebaseer op ‘n 300 ton suikerriet/h (81 ton bagasse/h) plantasie-grote. Ten slotte, vanuit ‘n ekonomiese oogpunt, blyk ‘n biomassa verbranding gebaseer op die 63 bar CEST BMECP model die mees ekonomies-vatbare opsie onder huidige ekonomiese omstandighede. Eerste orde totale kapitale belegging beraming vir hierdie BMECP is ongeveer $116 miljoen, produksie NPV is$390 miljoen aan die einde van ‘n 20 jaar tydperk vir ‘n suikerriet-aanleg. IRP is 34.51%. Die Suiwer Vinnige Pirolise BMECP is die mins-ekonomiese vatbare model. Sensitiewiteits-analises het getoon dat hierdie BMECP model baie sensitief is ten opsigte van verandering in die pryse van bagasse en elektrisieteit; in die geval van NPV is veranderinge van -191.61/+446.86% aangedui op ‘n ±30% verandering in bagasse pryse. In die geval van elektrisieteitspryse, is ‘n sensitiewiteit van van -91.5/+338.60% op ‘n ±30% prysverandering getoon

СОНОХИМИЧЕСКОЕ МОДИФИЦИРОВАНИЕ ПОВЕРХНОСТИ НИКЕЛЯ МОЛИБДЕНОВОЙ КИСЛОТОЙ И ПРОДУКТАМИ ЕЕ ПОЛИКОНДЕНСАЦИИ

The possibility of sonochemical immobilization of polymolybdic acid on the surface of electrochemically deposited nickel is shown. It is revealed that the thus obtained oxide-hydroxide surface layer is inhomogeneous and involves the products of interaction of molybdic acid oligomers with nickel and MoO3 particles which impart antifriction properties to the modified nickel surface. The possibility of doping the sonochemically obtained molybdenum oxide-hydroxide layer with a corrosion inhibitor (benzotriazole) is demonstrated; such treatment results in a radical (ca. 4-fold) enhancement of corrosion resistance of the galvanic nickel coating.Показана возможность сонохимической иммобилизации продуктов поликонденсации молибденовой кислоты к поверхности электрохимически осажденного никеля. Установлено, что формирующаяся при этом оксидно-гидроксидная пленка является фазово неоднородной и включает не только продукты химического взаимодействия олигомеров молибденовой кислоты с поверхностью никеля, но и дискретные частицы триоксида молибдена, которые придают поверхности никеля антифрикционные свойства. На примере бензотриазола продемонстрирована возможность допирования сонохимически осажденных оксидно-гидроксидных пленок ингибиторами коррозии. Такое модифицирование кардинальным образом (до 4 раз и более) увеличивает защитно-коррозионные свойства никелевого покрытия

ЭЛЕКТРОХИМИЧЕСКИЙ СИНТЕЗ МЕТАЛЛ-МАТРИЧНЫХ КОМПОЗИТОВ НА ОСНОВЕ ДИСПЕРСНЫХ ЧАСТИЦ МоО3/WO3 СО СТРУКТУРОЙ «ЯДРО–ОБОЛОЧКА»

The possibility of synthesis of metal-matrix composites via coprecipitation of nickel with the particles of МоО3 (core)–WO3(shell) structure was demonstrated. It has been shown that the deposition of WO3 shell permits one to stabilize the dispersed molybdenum trioxide in the nickel plating bath, with the particles of second phase retaining the redox activity that facilitates their overgrowing with matrix metal and ensures large oxide loading in the nickel deposit at a low concentration of oxide in the electrolyte. It is shown that due to the lamellar structure inherent in the MoO3 core the Ni–MoO3/WO3 composites exhibit enhanced wear resistance that is more than 3 times as high as that of bare galvanic nickel.Продемонстрирована возможность получения металл-матричных композитов за счет соосаждения никеля с частицами типа «ядро (МоО3)–оболочка (WO3)». Показано, что нанесение оболочек из триоксида вольфрама позволяет стабилизировать дисперсный триоксид молибдена в растворах электрохимического никелирования при сохранении частицами редокс-активности, что положительным образом сказывается на враста- нии частиц дисперсной фазы в металлическую матрицу и позволяет обеспечить высокое содержание оксида в никелевом покрытии при его небольшой концентрации в электролите. Показано, что благодаря слоистому строению частиц дисперсной фазы композиты Ni–MoO3/WO3 характеризуются высокими уровнями износостойкости (превышающим износостойкость гальванического никеля более чем в 3 раза)

ЭЛЕКТРОХИМИЧЕСКОЕ СООСА ЖДЕНИЕ НИКЕЛЯ И ЧАСТИЦ ТРИОКСИДА МОЛИБДЕНА С РЕГУЛИРУЕМОЙ РЕДОКС -АКТИВНОСТЬЮ

It is shown that the redox-activity of dispersed molybdenum trioxide can be controlled by deposition of silica onto the surface of oxide particles. The redox-activity of the core-shell type particles obtained governs the mechanism of incorporation of second-phase particles into the metal matrix. This, in turn, affects the surface morphology as well as tribological and corrosion resistance properties of the metal-matrix composites obtained.Показано, что редокс-активностью дисперсного триоксида молибдена можно управлять путем нанесения на поверхность его частиц диоксида кремния. Редокс-активность получаемых таким образом частиц типа «ядро–оболочка» определяет механизм их инкорпорирования в металлическую матрицу, что, в свою очередь, оказывает влияние на морфологию поверхности, а также трибологические и коррозионные свойства осаждаемых металл-матричных композитов

СОЛЬВОТЕРМИЧЕСКИЙ СИНТЕЗ МОЛИБДЕН-ВАНАДИЕВЫХ КАТАЛИЗАТОРОВ НА НОСИТЕЛЯХ ИЗ ДИОКСИДА КРЕМНИЯ

The possibility of solvothermal deposition of mixed oxide of molybdenum-vanadium on an inert silica carrier (mesoporous grains, nanoparticles) via the polycondensation of mixed molybdenum- vanadium acid under controlled conditions has been demonstrated. It is shown that the obtained catalysts representing the solid V2O5 : MoO3 solution exhisit the high activity in the reaction of thiophene oxidation at 250 °С and can be used for desulphation of hydrocarbons.Продемонстрирована возможность сольвотермического осаждения смешанного оксида молибдена-ванадия на инертный носитель из диоксида кремния в виде мезопористых гранул и наночастиц за счет поликонденсации смешанной молибден-ванадиевой кислоты в контролируемых условиях. Показано, что полученные нанесенные катализаторы, представляющие собой твердый раствор V2O5 : MoO3, характеризуются высокой активностью в реакции окисления тиофена при температуре 250 °С, что позволяет использовать их в качестве основы перспективных систем десульфирования углеводородного сырья

Создание рН-чувствительных антикоррозионных контейнерных систем на основе частиц интеркалированного азолом оксида молибдена с олигооксометаллатной оболочкой

The container structures consisting of the core made of layered molybdenum oxide intercalated with 3-amono-1,2,4-triazole (it behaves as the corrosion inhibitor) capped with the shell made of polymerized tungsten oxide were synthesized employing the polycondensation of oxocompounds. It is shown that in the acid (pH &lt; 5.5) and alkali (pH &gt; 8.5) media, the coating continuity appears to be broken reversibly, which facilitates the emission of the encapsulated compounds from the containers. The intrinsic redox activity inherent into the oligooxometalate shell permits one to immobilize the synthesized containers by co-precipitation with galvanic nickel, whereas the possibility to open the container as a result of local pH value variations accompanying the corrosion process ensures the autonomic corrosion protection of the resultant metal-matrix coatings.С использованием процессов поликонденсации оксосоединений синтезированы контейнерные структуры в виде ядра из слоистого триоксида молибдена, интеркалированного 3-амино-1,2,4-триазолом (ингибитор коррозии), на поверхность которого нанесена оболочка из полимеризованной вольфрамовой кислоты. Показано, что в кислой (pH &lt; 5,5) и щелочной (pH &gt; 8,5) среде сплошность оболочки обратимо нарушается, что позволяет инкапсулированному содержимому выделяться в окружающую среду. Наличие у оксометаллатной оболочки собственной редокс-активности позволяет иммобилизовать содержащие ингибитор контейнерные структуры за счет электрохимического соосаждения с никелем, а возможность открытия контейнеров в результате изменения локальных значений рН при протекании коррозионного процесса обеспечивает автономную антикоррозионную защиту полученных металл-матричных покрытий